Residential and commercial irrigation systems for turf and landscaping typically include one or more solenoid operated valves that are turned ON and OFF by an electronic irrigation controller. The valves admit water to various branch lines in the form of subterranean PVC pipes that each supply several sprinklers connected at spaced intervals. Each combination of a solenoid valve and its associated sprinklers is referred to in the irrigation industry as a zone or station. A modern electronic irrigation controller typically includes a microprocessor that executes one or more stored watering programs. These watering programs are typically programmed or selected by the user via push button and/or rotary knob. The irrigation controller usually has an LCD or other display to facilitate programming by the user. The microprocessor controls the solenoid valves via suitable drivers and switching devices. The valves are opened and closed by the microprocessor in accordance with the programmed run and cycle times for each of the stations.
Modular expandable irrigation controllers have gained increasing popularity in both residential and commercial landscape applications. In a modular irrigation controller, the base portion of the irrigation controller contains the microprocessor and user actuated manual controls. Each station is then controlled by a corresponding station module which comprises a plastic housing that encloses and supports a station module circuit, as well as wire connection terminals for connecting wires that lead to a plurality of solenoid actuated irrigation valves. Typically each station module can independently control more than one solenoid actuated valve. The station modules contain pins, sockets, card edge connectors or some other standard form of electro-mechanical connectors for allowing them to be connected and disconnected from the base portion of the irrigation controller. The station modules are typically inserted into receptacles in either the housing that contains the microprocessor or a separate back panel hinged to the microprocessor housing. A modular irrigation controller is typically connected to each solenoid actuated valve by a dedicated field valve line, for example, twelve gauge wire. A common return line is connected between all of the valves and the irrigation controller. Triacs in the station module circuit are typically used to switch a twenty-four volt AC signal ON and OFF relative to each of the field valve lines.
The principal advantage of this modular configuration is that the base portion of the irrigation controller need only be equipped with the minimum number of station modules that can control the total number of stations required to irrigate the turf and/or landscaping of a particular system installation. Thus, for example, an irrigation system may have only three zones, requiring only a single station module, while another may have twelve zones that might require four station modules. Considerable cost savings are thus achieved. Moreover, if an irrigation system expands after initial installation because the landscaping has increased, additional station modules can be added. Furthermore, if a station module is damaged by a lightening strike, or otherwise fails, it can be readily replaced.
One drawback of conventional modular irrigation controllers is that the user typically connects the field valve lines to the station modules when the AC power to the modules is “live,” presenting a shock hazard. If an indoor mounted controller is first disconnected from the AC wall outlet, there is a risk that the watering programs stored in the controller will be lost. Outdoor mounted controllers are usually hard-wired to an AC power source. To reduce the risk of an electric shock, the user must first locate and turn off a circuit breaker, typically at a remote and inconvenient location, before connecting or reconnecting field valve line wires. Again, there is a risk of losing the watering programs when the power is shut off to the irrigation controller in this fashion. This drawback has been overcome by constructing the modular irrigation controller such that only the communication path to the processor is established when the modules are plugged in, and thereafter, power is applied to the modules when they are locked in place. See U.S. Pat. No. 7,225,058 granted to La Monte D. Porter on May 29, 2007, assigned to Hunter Industries, Inc.
Yet another problem with conventional modular controllers is that power is constantly being provided to the microprocessor, which is often mounted in a removable face pack. Many times users would like to temporarily remove power to the face pack in order to perform various maintenance or service, such as replacement of a face pack where it is damaged or in order to upgrade the face pack. In conventional outdoor irrigation controllers the primary power is wired directly into the controller which is usually a sealed, highly flame-retardant enclosure. Removing the power to the face pack of such an irrigation controller requires the user to either open this enclosure and disconnect high voltage wiring from a transformer, or cut the secondary leads of the transformer.